Assessing the most powerful analysis method for school-based intervention studies with alcohol, tobacco, and other drug outcomes

Jessica B. Janega, David M. Murray, Sherri P. Varnell, Jonathan L. Blitstein, Amanda S. Birnbaum, Leslie A. Lytle

Research output: Contribution to journalArticle

17 Scopus citations


This article compares four mixed-model analyses valid for group-randomized trials (GRTs) involving a nested cohort design with a single pretest and a single posttest, the most common design used in GRTs. This study makes estimates of intraclass correlations (ICCs) available to investigators planning GRTs with alcohol, tobacco, and other drug measures as the outcomes of interest. It also provides formulae demonstrating the potential benefits to the standard error of the intervention effect of both adjustments for fixed and time-varying covariates, as well as correlations over time. These estimates will allow other researchers using these variables to plan their studies by performing a priori power analyses for any of four common analytic options.

Original languageEnglish
Pages (from-to)595-606
Number of pages12
JournalAddictive Behaviors
Issue number3
StatePublished - 1 May 2004



  • ATOD prevention
  • Group-randomized trial
  • Intraclass correlation
  • Power
  • School based

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